Objective optical element, optical pick-up apparatus, and optical information recording reproducing apparatus

Abstract

An objective optical element for use in an optical pickup apparatus, includes an objective lens to converge the light flux emitted from the first and second light sources; and an optical functional surface including a common region and an exclusive region. When a first optical information medium is used, a sine condition unsatisfied-amount whose value is maximum exists on the common region. The following formula is satisfied:0.5≦COMA2 / COMA1≦1.0where COMA1 is a coma aberration (λ1 rms) when a light flux goes slantingly to be incident with a view angle of 1° onto the objective optical element when the first optical information medium is used, and COMA2 is a coma aberration (λ2 rms) when a light flux goes slantingly to be incident with a view angle of 1° onto the objective optical element when the second optical information medium is used.

Description

BACKGROUND OF THE INVENTIONThe present invention relates to an objective optical element used for an optical pick-up apparatus by which the recording / reproducing of an optical information recording medium whose operating wavelength is different and transparent substrate thickness is different is conducted by one objective lens, and optical pick-up apparatus and optical information recording reproducing apparatus, and particularly to the objective optical element in which a light source portion which oscillates the different wavelength is used for the modularized light source (2-laser 1 package module), or used for an optical system in which the focal length of the objective lens is short and which is sensitive to the error factors, and in which the image height coma characteristic at the time when each optical information recording medium is used, is improved, and the optical pick-up apparatus using it, and the optical information recording reproducing apparatus.Nowadays, many kinds...

AI Technical Summary

Benefits of technology

In view of the above-described problems, the present invention is attained, and the object of the present invention is to provide an objective optical element for the optical pick-up apparatus by which the coma can be corrected with good balance, and the recording or reproducing of the information can be adequately conducted onto the different optical information recording media, and the optical pick-up apparatus and the optical information recording reproducing apparatus.

An optical information recording reproducing apparatus described in Item 94 is the optical information recording reproducing apparatus having: the first light source of the wavelength λ1 by which the recording or reproducing of the information is conducted by irradiating the light flux onto the first optical information recording medium whose transparent substrate thickness is t1; the second light source of the wavelength λ2 (λ1<λ2) by which the recording or reproducing of the information is conducted by irradiating the light flux onto the second optical information recording medium whose transparent substrate thickness is t2 (t1<t2); and the light converging optical system including the objective optical element by which the light fluxes out-gone from the first and the second light sources are converged onto the information recording surface through the transparent substrates of the first and the second optical information recording media; and the objective optical element has: an objective lens to converge the light flux from the first light source or the second light source, and the optical function surface to give the optical action to the light flux; on the optical function surface of the light source side of the objective optical element, the diffractive structure making the optical axis a center of rotation is provided; on the optical function surface of the optical information recording medium side of the objective optical element, a common region which includes the optical axis, and is used for the recording and / or reproducing of the information onto both of the first optical information recording medium and the second optical information recording medium, and the exclusive region which is provided outside the common region and is used for the recording and / or reproducing of the information mainly onto the first optical information recording medium, and a step difference portion which adjoins the common region and the exclusive region, and which is almost parallel to the optical axis and faces outside to the optical axis, are provided; and because the objective optical element forms the spot diameter on the first optical information recording medium determined from the effective diameter and the focal length of the objective optical element, in the first optical information recording medium, the same effect as the invention described in Item 22 can be attained.

Problems solved by technology

However, as the optical characteristic deterioration factor to obstacle the recording or reproducing of the adequate information, the coma also exists other than the spherical aberration.

In the case where the coma is large, when the light flux tilted to the optical axis is incident, by the inclination of the objective lens generated due to the assembling error, there is a possibility that the formation of the adequate spot on the optical information recording medium is obstructed.

However, when the above-described diffractive structure is used, both of the spherical aberrations at the time when both of the DVD / CD are used, can be reduced, but for the coma, there is a problem that the both can not be simultaneously corrected.

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